LOW-PRESSURE CHEMICAL-VAPOR-DEPOSITION OF MOLYBDENUM OXIDES FROM MOLYBDENUM HEXACARBONYL AND OXYGEN

Thin films of molybdenum oxides were deposited at 300-500 degrees C and 200-1014 mTorr (26.6-135 Pa) from Mo(CO)(6), O-2, and H2O using an inductively heated low pressure chemical vapor deposition system. Two oxygen gas flow rates of 5 and 15 seem were used. alpha-MoO3 films were deposited at temperatures of 425-450 degrees C, pressures of 660-1014 mTorr (88.0-135 Pa), with an O-2 flow rate of 5 seem; and at 450-500 degrees C, 300-500 mTorr (40.0-66.7 Pa), with an O-2 flow rate of 5 seem. The polycrystalline films were deposited on silicon (100) wafers and exhibited preferred orientations. Gas phase decomposition of the precursor was significant with temperatures >400 degrees C and pressures >600 mTorr (88.0 Pa), with an O-2 flow rate of 15 seem. Owing to decomposition of the precursor in the gas phase and low gas velocities, the films decreased in thickness in the direction of flow. Thermodynamic equilibrium calculations indicated that alpha-MoO3 was the most stable phase for all deposition conditions. However, alpha-MoO3 was deposited only at high temperatures and pressures. A quadratic model of alpha-MoO3 formation was developed using experimental design for the 5 seem deposition data as a function of temperature and pressure. Both parameters were significant in the formation of alpha-MoO3 films. The films were characterized using X-ray diffraction and X-ray photoelectron, Auger, and laser Raman spectroscopies.